Issue date: 26 July 2001

Small quantities of oestrogens, which are female hormones, are excreted from the body and thus enter the sewage system. Although these chemicals seem to be largely removed in sewage treatment, it seems that minute quantities remain and thus can enter rivers to which treated sewage is discharged. These very low levels of oestrogens have been shown to be responsible for signs of sex changes in male fish in rivers to which sewage is discharged - they begin to show some female characteristics. Now, scientists at the University of the West of England (UWE) have developed highly sensitive chemical analysis procedures that can detect minute traces of these hormones.

The project is a collaboration between UWE and the Environment Agency, and involves taking samples of water from the Thames in London. The samples are separated into their constituent parts using a technique called gas chromatography-negative chemical ionisation mass spectrometry. The techniques developed can also distinguish whether the hormones present are naturally occurring or result from use of the contraceptive pill.

"We can now detect quantities of oestrogens down to levels equivalent to a pinch of sugar in an Olympic swimming pool," says Dr David McCalley, who has been leading the project. "Our method is sensitive enough to allow direct chemical measurements of oestrogens in rivers, rather than measuring them indirectly through their biological effects".

"We discovered that the largest concentrations in the River Thames are of naturally produced oestrogens. We have not been able to detect any synthetic oestrogens, which would derive from the pill."

Increases in the level of oestrogens in river water have been cited as a possible cause of decreasing levels of male fertility, although it seems very likely that oestrogens are removed during the treatment of water for drinking purposes.

The project has now successfully been completed and results have recently been published in the Journal of Chromatography A.


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